(1) Field of the Invention
The present invention relates to a Schottky barrier diode. The present invention especially relates to a low-loss Schottky barrier diode which achieves a lower forward voltage Vf and a smaller capacitance, without an increase in a reverse leakage current.
(2) Prior Art
In recent years, Schottky barrier diodes are widely used as rectifying elements in electronic products in order to achieve lower power consumption and higher speed. Schottky barrier diodes have a lower forward voltage Vf and a smaller capacitance than general pn-junction diodes.
A forward voltage Vf of a Schottky barrier diode decreases as a barrier height is lowered. However, a decrease in Schottky barrier height causes a problem that reverse currents that are generated when a reverse bias is applied, i.e. a leakage current, increase.
To solve this problem, unexamined Japanese patent application publication No. H11-330498 discloses a Schottky barrier diode (herein after referred to as a conventional Schottky barrier diode).
This conventional Schottky barrier diode has the following constitution. A metal anode electrode is provided on a surface of a semiconductor layer of a first conductivity type, so as to form a Schottky contact. An ohmic cathode electrode is provided on an opposite surface of the semiconductor layer of the first conductivity type. Semiconductor layers of a second conductivity type are buried within the semiconductor layer of the first conductivity type, at such intervals that depletion layers formed at interface regions between the buried layers and the semiconductor layer connect with one another when a reverse bias is applied. The semiconductor layers of the second conductivity type (hereinafter referred to as buried layers) are at the same potential as the anode electrode forming the Schottky contact.
According to the above construction, the buried layers formed within the semiconductor layer of the first conductivity type are at the same potential as the anode electrode. Therefore, when a reverse bias is applied, depletion layers formed at interface regions between the buried layers and the semiconductor layer of the first conductivity type expand. The expansion of the depletion layers reduces a leakage current.
However, since the buried layers are buried within the semiconductor layer of the first conductivity type, a passage area for carriers that cross a Schottky contact barrier when a forward voltage is applied decreases. This causes a resistance to be generated, and therefore causes a forward voltage Vf of the above-mentioned conventional Schottky barrier diode to increase.
Furthermore, a speed of a switching operation is decreased by a capacitance of the depletion layers formed at interface regions between the buried layers at the same potential as the anode electrode and the semiconductor layer of the first conductivity type at the same potential as the cathode electrode.